Agilent 5890 GC problems

We currently have three Agilent 5890 GC systems. We have also recently upgraded to Empower 3 FR2 from Empower 2.Under Empower 2, we were using bus-LAC/E cards to connect the GCs. We had no issues with this. Under Empower 3, we purchased an Avocent 8 port serial hub to connect our GCs. We have followed everything outlined in this document: https://www.google.com/url?sa=t&rct=j&q=&esrc=s&source=web&cd=1&cad=rja&uact=8&ved=0CB0QFjAA&url=http%3A%2F%2Fwww.waters… to the best of our knowledge.We are unable to run more than one GC at a time without one (or all) of the GCs stopping part of the way through a sequence. No error messages are given. Does anyone have any suggestions?